Chemical flooding is one of the most effective and potential chemical technologies for Enhanced Oil Recovery, which is especially represented by polymer flooding. However, there arise some problems for conventional polymers along with the deep implementation of polymer flooding technology. Under reservoir conditions of high temperature and high salinity, the viscosifying capacity and thermal stability of the widely used polymer, partially hydrolyzed polyacrylamide (HPAM), reduces rapidly; in the meantime, HPAM does not have the surface/interfacial activity per se, and could not start the oil film effectively, so that its ability to mine the remaining oil is limited. The polymer-based binary-component composite system (polymer/surfactant) and triple-component system (polymer/surfactant/alkali) may enhance the stability of the emulsified produced fluid, resulting in increased difficulty in oil/water separation and sewage treatment, as well as the weakening of synergistic effect among the components of the system under reservoir conditions, and also it may damage the reservoir. The application of the composite system is thus restricted.
It has become a difficulty and key for many large oilfield developments to keep the viscosifying capacity and viscosity stability of the polymer solution, so as to achieve the strategic target of stabilization of oil production and water cut control.
Heavy oil is a collective name for unconventional oil, including heavy oil, high viscosity oil, oil sand, natural asphalt and etc., and they are also referred to as heavy oil, ultra-heavy oil, asphalt and etc. Among the approximate 10 trillion barrels of remaining oil resources around the world, more than 70% of which is heavy oil resource. Chinese onshore heavy oil and bitumen resources account for about more than 20% of their total oil resources. According to incomplete statistics, the proved and controlled heavy oil reserves in China reach 1600 million tons. Nowadays heavy oil resource has become one of the important strategic replacement resources in China; however, the exploitation of heavy oil is rather difficult. Chemical emulsification and viscosity reduction method has become an important exploitation technology.
Polymeric emulsification viscosity reducer usually refers to a polymeric surfactant with a relative molecular weight more than several thousands and significant surface activity; according to the ion types, it can be divided into four categories: anionic, cationic, zwitterionic and non-ionic polymeric surfactant. Polymeric surfactant usually has limited capacity to reduce surface tension and oil-water interfacial tension, but has excellent emulsification and dispersion capability for heavy oil, with advantages of small usage amount, high viscosity reduction rate, lower cost and simple implementation process. In recent years, this research especially attracts more and more attention in this field.